Liver Histopathology

Liver biopsy specimens were obtained using a 14‐gauge modified Vim Silverman needle (Tohoku University style; Kakinuma Factory, Tokyo, Japan), a 16‐gauge core tissue biopsy needle (Bard Peripheral Vascular, Inc., Tempe, AZ), or surgical resection. Liver biopsy samples >1.5 cm and/or containing more than 11 portal tracts were considered adequate for examination and diagnosis. The specimen was fixed in 10% formalin and cut into sections, which were then stained with hematoxylin and eosin, Masson trichrome, silver impregnation, or periodic acid–Schiff after diastase digestion. Four pathologists (Dr. Keiichi Kinowaki, Dr. Fukuo Kondo, Dr. Toshio Fukusato, and Dr. Takeshi Fujii), who were blinded to the clinical findings evaluated each of the specimens, and the final assessment was reached by consensus.

Steatosis grades 0, 1, 2, and 3 corresponded to steatosis of <5%, ≥5% to <33%, ≥33% to <66%, and ≥66% of hepatocytes, respectively. Lobular inflammation with no foci, <2 foci, 2‐4 foci, and ≥4 foci per 200× field was scored 0, 1, 2, and 3, respectively. Hepatocyte ballooning of none, few, and many cells was scored as 0, 1, and 2, respectively. NAS represents the sum of scores of steatosis, lobular inflammation, and hepatocyte ballooning (range, 0‐8 points).¹⁴ Fibrosis stage was defined as 0, 1, 2, 3, and 4 using the defined criteria.¹⁴, ¹⁵ NASH was defined according to the fatty liver: inhibition of progression (FLIP) algorithm.¹⁶